[WebUI] ClosureCompile cr.ui.DragWrapper, create a real handler class

chrome/browser/resources/extensions/drag_and_drop_handler.js

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+cr.define('extensions', function() {
+  'use strict';
+
+  /**
+   * @param {boolean} dragEnabled
+   * @param {!EventTarget} target
+   * @constructor
+   * @implements cr.ui.DragWrapperDelegate
+   */
+  function DragAndDropHandler(dragEnabled, target) {
+    this.dragEnabled = dragEnabled;
+    /** @private {!EventTarget} */
+    this.eventTarget_ = target;
+  }
+
+  // TODO(devlin): Un-chrome.send-ify this implementation.
+  DragAndDropHandler.prototype = {
+    /** @type {boolean} */
+    dragEnabled: false,
+
+    /** @override */
+    shouldAcceptDrag: function(e) {
+      // External Extension installation can be disabled globally, e.g. while a
+      // different overlay is already showing.
+      if (!this.dragEnabled)
+        return false;
+
+      // We can't access filenames during the 'dragenter' event, so we have to
+      // wait until 'drop' to decide whether to do something with the file or
+      // not.
+      // See: http://www.w3.org/TR/2011/WD-html5-20110113/dnd.html#concept-dnd-p
+      return !!e.dataTransfer.types &&
+             e.dataTransfer.types.indexOf('Files') > -1;
+    },
+
+    /** @override */
+    doDragEnter: function() {
+      chrome.send('startDrag');
+      this.eventTarget_.dispatchEvent(
+          new CustomEvent('extension-drag-started'));
+    },
+
+    /** @override */
+    doDragLeave: function() {
+      this.fireDragEnded_();

[Dan Beam, 2016/07/21 23:42:39]

i think it's odd to say the drag has ended if this really just means the user
has moved the mouse (while still down) out of the area we consider valid.  but
you're basically just using this like a private event channel, so I suppose it's
fine.

+      chrome.send('stopDrag');
+    },
+
+    /** @override */
+    doDragOver: function(e) {
+      e.preventDefault();
+    },
+
+    /** @override */
+    doDrop: function(e) {
+      this.fireDragEnded_();
+      if (e.dataTransfer.files.length != 1)
+        return;
+
+      var toSend = '';
+      // Files lack a check if they're a directory, but we can find out through
+      // its item entry.
+      for (var i = 0; i < e.dataTransfer.items.length; ++i) {
+        if (e.dataTransfer.items[i].kind == 'file' &&
+            e.dataTransfer.items[i].webkitGetAsEntry().isDirectory) {
+          toSend = 'installDroppedDirectory';
+          break;
+        }
+      }
+      // Only process files that look like extensions. Other files should
+      // navigate the browser normally.
+      if (!toSend &&
+          /\.(crx|user\.js|zip)$/i.test(e.dataTransfer.files[0].name)) {
+        toSend = 'installDroppedFile';
+      }
+
+      if (toSend) {
+        e.preventDefault();
+        chrome.send(toSend);
+      }
+    },
+
+     /** @private */
+    fireDragEnded_: function() {
+      this.eventTarget_.dispatchEvent(new CustomEvent('extension-drag-ended'));
+    }
+  };
+
+  return {
+    DragAndDropHandler: DragAndDropHandler,
+  };
+});